We go every two years in Sept. and love it. It is very warm though, usually in the upper 80's to mid 90's F. Expect an afternoon downpour, but these don't last very long. I buy a supply of the disposable rain ponchos and always carry one for each of us. We wear them untill the rain stops and then throw them away and enjoy the rest of the day.
If you don't let the weather get you down and just roll with it you will be just fine.....Remember to drink LOTS of water.